In general, thin film manufacturing methods such as chemical vapor deposition (CVD), atomic layer deposition (ALD) and the like are used to deposit a thin film with a predetermined thickness over a substrate such as a semiconductor wafer or glass. Among these methods, ALD has been expected to be a next-generation method of depositing a thin film, because the ability to control the deposition process is excellent. In an ALD process, a chemically reactive gas is supplied to deposition equipment, in a similar fashion to CVD. When a film is deposited by CVD, all reaction substances together form a thin film when exposed to the surface of a wafer. When a film is deposited by the ALD method, reaction substances are separately supplied in pulses, and isolated from one another by a purge gas. The pulse of each reaction substance causes a delicate single-layered film growth by causing a chemical reaction with the surface of a wafer. Since the ALD method has the advantage of self-limiting reactions, a precise film thickness control may be realized.
Referring to FIG. 1, the ALD equipment 110 includes: a chamber 111 containing a sample 100 such as a wafer positioned therein, the chamber defining a reaction space above the sample 100; a supply line 112 through which a raw material gas is supplied into the reaction space; and an exhaust line 113 through which a reaction gas within the reaction space of the chamber 111 is exhausted to a pumping system. In the drawing, arrows within the chamber 111 indicate the movement of gas.
When a thin film is deposited, the ALD equipment does not collect or produce information on reactions occurring within the chamber during the deposition process. The resulting thin film substance may be identified through various physical property measurements only after the deposition has been ended. Accordingly, precise process control during thin film deposition, e.g., control of raw material supply or a thin film property is made more difficult.